Arginine and other basic amino acids have been proposed for use in oral care and are believed to have significant benefits in combating cavity formation and tooth sensitivity. Combining these basic amino acids with minerals having oral care benefits, e.g., fluoride and calcium, to form a mouthwash presents challenges. For example, the basic amino acid tends to raise the pH, but at higher pH, the mineral ions such as fluoride and calcium tend to form salts and to be less available for delivery to the teeth. Moreover, the higher pH has the potential to cause irritation in the mouth. At neutral pH or acidic pH, however, a system utilizing arginine bicarbonate (which the art teaches is preferred and which is found in marketed arginine-based oral care products) may release carbon dioxide, leading to bloating and bursting of the containers upon storage. Other formulation excipients, such as betaine (trimethyl glycine) have oral care benefits in some applications, but like arginine, tend to raise the pH of the formulation.
Another issue with mouthwash formulations is the difficulty of making formulations comprising enzymes, as the enzymes may be pH sensitive and may react with the formulation excipients.
Formulations comprising bleaching agents present further difficulties, as bleaching agents may be more stable at higher pH but more effective at lower pH.
Thus, there is frequently a problem that the optimum pH for formulation stability of a particular mouthwash formulation is quite different from the optimum pH for delivery of beneficial agents from the mouthwash. There is a need for a stable mouthwash product that provides a stable formulation, yet also provides efficient delivery of beneficial agents such as fluoride, calcium, and basic amino acids, and pH-sensitive agents like enzymes and bleaches.